Search results for " coordinate system"
showing 10 items of 77 documents
MEASUREMENT OF THE TAU-POLARIZATION AT THE Z-RESONANCE
1993
Using 18.8 pb-1 of data collected in 1990 and 1991, ALEPH has measured the tau polarisation in the decay modes tau-->enunuBAR, tau-->mununuBAR, tau-->rhonu tau-->a1nu, using both the individual tau decay kinematics and the event acollinearity. The measurement of the tau polarisation as a function of the production polar angle yields the two parameters A(tau) and A(e), where A(l) = 2g(V)l g(A)l/[(g(V)l)2 + (g(A)l)2]. The results A(tau) = 0.143 +/- 0.023 and A(e) = 0. 120 +/- 0.026 are consistent with the hypothesis of electron-tau universality. Assuming universality yields a measurement of the effective weak mixing angle sin 2theta(W)eff = 0.2332 +/- 0.0022.
Forward tracking at the nexte+e−collider. Part I. The physics case
2009
n a series of notes we explore the detector requirements of the forward tracking region for a future e(+)e(-) collider with a center-of-mass energy in the range from 500 GeV to 3 TeV. In this first part we investigate the relevance of the forward region for a range of physics processes that are likely to be relevant in such a machine. We find that many examples can be found where excellent performance of the forward detector system may lead to a considerable increase of the physics output of the experiment. A particularly clear physics case can be made for the reconstruction of electrons at small polar angle.
Monte Carlo calculation of dose rate distributions around the Walstam CDC.K-type137Cs sources
2001
Basic dosimetric data for the Walstam CDC.K-type low dose rate 137Cs sources in water have been calculated using Monte Carlo techniques. These sources, CDC.K1 -K3 and CDC.K4, are widely used in a range of applicators and moulds for the treatment of intracavitary and superficial cancers. Our purpose is to improve existing data about these sources using the Monte Carlo simulation code GEANT3. Absolute dose rate distributions in water have been calculated around these sources and are presented as conventional 2D Cartesian look-up tables. Also the AAPM Task Group 43 formalism for dose calculation has been applied. The calculated dose rate constant for the CDC.K1-K3 source is A = 1.106 +/- 0.001…
Maximal slicings in spherical symmetry: Local existence and construction
2011
We show that any spherically symmetric spacetime locally admits a maximal spacelike slicing and we give a procedure allowing its construction. The construction procedure that we have designed is based on purely geometrical arguments and, in practice, leads to solve a decoupled system of first order quasi-linear partial differential equations. We have explicitly built up maximal foliations in Minkowski and Friedmann spacetimes. Our approach admits further generalizations and efficient computational implementation. As by product, we suggest some applications of our work in the task of calibrating Numerical Relativity complex codes, usually written in Cartesian coordinates.
Monte Carlo dosimetry of the Buchler high dose rate 192Ir source.
2001
In this study a complete set of dosimetric data is presented for the high dose rate (HDR) source from Amersham used in the Buchler remote afterloading HDR unit. These data have been calculated by means of the Monte Carlo simulation code GEANT taking into account the detailed geometry of the source. Absolute dose rate distributions in water were calculated around this source and are presented as conventional 2D Cartesian look-up tables. All dosimetric quantities recommended by the AAPM Task Group 43 report have been calculated. Quantities determined are: dose rate constant, radial dose function, anisotropy function, anisotropy factor and anisotropy constant. The dose rate distributions of th…
Orbit determination and errors of a star catalogue
1995
Abstract We obtain Ceres orbit taking into account all perturbations and applying correction of phase effect to observations. More than 3000 observations have been used and the results agree with other determinations. We have also investigated the influence of systematic errors of a star catalogue on the observations and its effect on final elements. To that aim, a simulation procedure has been applied to Ceres observations, including different laws for errors of star catalogue versus spherical coordinates. The best relations have been applied to real observations of Ceres, in order to obtain elements and star catalogue corrections. Preliminary results of these calculations are presented.
Grid-based Methods in Relativistic Hydrodynamics and Magnetohydrodynamics
2015
An overview of grid-based numerical methods used in relativistic hydrodynamics (RHD) and magnetohydrodynamics (RMHD) is presented. Special emphasis is put on a comprehensive review of the application of high-resolution shock-capturing methods. Results of a set of demanding test bench simulations obtained with different numerical methods are compared in an attempt to assess the present capabilities and limits of the various numerical strategies. Applications to three astrophysical phenomena are briefly discussed to motivate the need for and to demonstrate the success of RHD and RMHD simulations in their understanding. The review further provides FORTRAN programs to compute the exact solution…
Time-of-arrival, angle-of-arrival, and angle-of-departure statistics of a novel simplistic disk channel model
2011
This paper introduces a novel simplistic geometrical disk scattering model in which the local scatterers are uniformly distributed in polar coordinates within a disk centered on the mobile station (MS). The proposed joint uniform distribution in polar coordinates results in a higher concentration of scatterers around the disk center and a lower concentration far from it. Furthermore, it is assumed that the base station (BS) is elevated to a non-scattering region and that a wave transmitted from the BS reaches the MS after a single bounce by one of the randomly distributed scatterers. Under the above-mentioned assumptions, we derive closed-form expressions for the joint probability density f…
A local picture associated with a triply degenerate vibrational mode: vibrational and rovibrational local states
1998
International audience; Abstract: A symmetrized basis adapted to the study of some vibrational excited states of spherical top molecules is proposed. This basis, consistent with the Cartesian picture associated with a three-dimensional mode, is then tested numerically through various XY6 and XY4 molecules. In addition, some simulations, made with 238UF6 and a simplified version of an effective Hamiltonian, clearly show that the method can be further extended through the construction of a symmetrized local rovibrational basis.
Dosimetric characteristics of the CDC-type miniature cylindrical 137Cs brachytherapy sources
2002
The low dose rate CDC-type miniature cylindrical 137 Cs sources are available, with one or three active beads, for use in source trains in automatic and manual afterloading systems for gynecological brachytherapy. Absolute dose rate distributions in water have been calculated around these sources using the Monte CarloGEANT3 code and they are presented as conventional two-dimensional Cartesian lookup tables. The AAPM Task Group 43 formalism for dose calculation has been also applied. The dose rate constant obtained for the one bead source is Λ=1.113±0.003 cGyh −1 U −1 , and the value for the three bead source is Λ=1.103±0.003 cGyh −1 U −1 . Finally, for the treatment planning systems based o…